This invention relates generally to valves for cargo tanks, and more particularly, to a high flow internal valves positioned substantially within the interior of a cargo tank.
Internal or emergency valves for liquid cargo tanks are known in the art. Examples of such valves are illustrated in U.S. Pat. Nos. 4,934,403 and 5,244,181, which are incorporated by reference herein. Internal valves are typically position in the bottom interior of the cargo tank and are designed for connection with a xe2x80x9cwet linexe2x80x9d which allows bottom loading and unloading of the cargo tank. As seen in U.S. Pat. No. 5,244,181, these internal valves have a main fluid flow passage through the valve. A rib extends across the fluid flow section but does not significantly disrupt the flow. A circular valve seat is formed around the entrance of the flow passage. A valve stem extends upwardly from the rib and a circular valve disk, which mates with and forms a seal with the valve seat, is slidingly mounted on the valve stem. When the valve disk is resting against the valve seat, the valve is closed. However, when the valve disk is lifted, such as by a mechanical lever as in U.S. Pat. No. 5,244,181, fluid can exit the cargo container through the flow passage.
While internal valves such as seen in U.S. Pat. No. 5,244,181 have served their purpose, there are many improvements which may be made. It would be advantageous to provide an internal valve which could be activated by a pressurized air source such as typically found on vehicles used to transport the cargo containers. It would also be advantageous to provide a manner of insuring gasoline or gasoline vapors did not migrate from the internal valve to the pressurized air system of the transport vehicle. Moreover, it would be an improvement in the art to provide a simple and reliable backup method of opening valve I in case the primary opening mechanism failed.
The present invention provides an air actuated internal valve for a cargo container. The valve generally comprises a valve base having a valve disk seat and a line connector extending therefrom. A valve stem having a first end is fixed to the valve base and a valve disk is slidingly mounted on the valve stem. A cylinder assembly is connected to the valve disk and a piston is positioned within the cylinder assembly and fixed to a second end of the valve stem. An air passage communicates through the base and the valve stem in order to provide air to an air space between the piston and a top internal portion of the cylinder assembly. When pressurized air is introduced into the air passage, the cylinder assembly (and thus the valve disk) moves upward, unseating the valve disk from the valve seat. This opens the valve and allows fluid to flow there through.